Before a total knee endoprosthesis, as these are known, for example, in DE-39 22 294 C1 and DE-41 41 757 C1, can be implanted, the bordering bone regions of the femur and tibia must be resected in an appropriate manner in order to provide standard mating surfaces corresponding to the predetermined geometry of the endoprosthesis. At present, the frontal aspects of the tibia and femur are generally resected. At the very least, the femur receives an additional so-called dorsal cut as well as a ventral cut, because the femur portions of the total endoprostheses in normal use today are so constructed as to fasten into the resulting resection surfaces (dorsal, ventral and frontal) in the fashion of a clamp.
The exact location of the resection lines in this regard is extremely difficult to choose.
Until now, the orientation of the tibia to the femur with a valgus angle of from 2.5.degree. to 7.5.degree. was accomplished in such cases by visual inspection by an operator with some experience in such operations. The template for the saw was then attached according to this placement and the resection carried out with an oscillating bone saw.
This admittedly requires substantial experience on the part of the operator. Beginners naturally have great difficulty, as do even very experienced operators under the stressful conditions of a surgical procedure.
It can be said that both the ventral and dorsal cuts in the femur bone must be so oriented that they run parallel to the frontal resection surface of the tibia, so that the total knee endoprosthesis is properly oriented along the axis. The endoprosthesis is properly oriented if no asymmetric stress on the joint occurs, which can lead to increased wear on one portion of the gliding surface of the tibial component of the endoprosthesis through the rebuilt condyles of the femoral component of the joint.